Abstract
Copper migration in the adhesive of NBR (acrylonitrile-butadiene copolymer) /epoxy resin blend system for flexible printed circuit board (FPC) is discussed by using the techniques of optical microscope, X-ray analytical microscope, transmission electron microscope, and ion chromatography. The accelerated migration test of FPC by the applied direct current voltage of 100V was carried out at 120°C under 100 % relative humidity. Because of high contents of inorganic anions such as SO42- in the NBR domain of the adhesive, migrated copper ions from anode selectively precipitated as fine particles of copper oxides in the NBR domain. Copper ions reached to the cathode without precipitating in the NBR domain deposited as dendrites in the vicinity of the cathode.
